Add Semigroup instance for 'Max' monoid

Otherwise ghc 8.4 will complain since Semigroup became a superclass
of Monoid.

src-brittany/Main.hs

@@ -11,6 +11,7 @@ import qualified Language.Haskell.GHC.ExactPrint.Annotate as ExactPrint.Annotate
 import qualified Language.Haskell.GHC.ExactPrint.Types as ExactPrint.Types
 import qualified Language.Haskell.GHC.ExactPrint.Parsers as ExactPrint.Parsers
 import qualified Data.Map as Map
+import qualified Data.Monoid
 
 import           Text.Read (Read(..))
 import qualified Text.ParserCombinators.ReadP as ReadP
@@ -148,7 +149,7 @@ mainCmdParser helpDesc = do
           , PP.text "inplace: override respective input file (without backup!)"
           ]
         )
-    <> flagDefault Display
+    Data.Monoid.<> flagDefault Display
     )
   inputParams <- addParamNoFlagStrings "PATH" (paramHelpStr "paths to input/inout haskell source files")
   reorderStop

src/Language/Haskell/Brittany/Internal/Prelude.hs

@@ -255,14 +255,16 @@ import Debug.Trace                   as E ( trace
 import Foreign.ForeignPtr            as E ( ForeignPtr
                                           )
 
-import Data.Monoid                   as E ( (<>)
-                                          , mconcat
+import Data.Monoid                   as E ( mconcat
                                           , Monoid (..)
                                           )
 
 import Data.Bifunctor                as E ( bimap )
 import Data.Functor                  as E ( (<$), ($>) )
 import Data.Function                 as E ( (&) )
+import Data.Semigroup                as E ( (<>)
+                                          , Semigroup(..)
+                                          )
 import System.IO                     as E ( hFlush
                                           , stdout
                                           )

src/Language/Haskell/Brittany/Internal/Utils.hs

@@ -84,9 +84,12 @@ fromOptionIdentity x y =
 newtype Max a = Max { getMax :: a }
   deriving (Eq, Ord, Show, Bounded, Num)
 
+instance (Num a, Ord a) => Semigroup (Max a) where
+  (<>) = Data.Coerce.coerce (max :: a -> a -> a)
+
 instance (Num a, Ord a) => Monoid (Max a) where
   mempty  = Max 0
-  mappend = Data.Coerce.coerce (max :: a -> a -> a)
+  mappend = (<>)
 
 newtype ShowIsId = ShowIsId String deriving Data